Method for in vitro glycoengineering of an erythropoiesis stimulating protein

ABSTRACT

The present invention relates to a method for the production of in vitro glycoengineered erythropoiesis stimulating protein, comprising the steps of providing sialic acid free erythropoiesis stimulating protein, treating the erythropoiesis stimulating protein with N-Acetyl-Glucosamin-transferase B3GNT2, treating the erythropoiesis stimulating protein with galactosyltransferase, and treating the erythropoiesis stimulating protein with sialyltransferase.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No. PCT/EP2018/056725, filed Mar. 16, 2018, which claims priority to European Patent Application No. 17161883.8, filed Mar. 20, 2017, each of which are incorporated herein by reference in its entirety.

SEQUENCE LISTING

This application contains a Sequence Listing which has been submitted electronically in ASCII format and is hereby incorporated by reference in its entirety. Said ASCII copy, created on Sep. 9, 2019, is named P34172-US-SeqList.txt and is 1,343,488 bytes in size.

FIELD OF THE INVENTION

The present invention relates to an in vitro glycoengineered erythropoiesis stimulating protein, methods for the production of said erythropoiesis stimulating protein and uses thereof.

BACKGROUND OF THE INVENTION

Erythropoiesis stimulating proteins are glycoproteins comprising several N-glycosylation sites. Variation of the glycan pattern on proteins has enormous implications on protein function. For example, the structure of the N-linked glycans on a protein can impact various characteristics, including the protease susceptibility, intracellular trafficking, secretion, tissue targeting, biological half-life and antigenicity of the protein in a cell or organism. The alteration of one or more of these characteristics greatly affects the efficacy of a protein in its natural setting, and also affects the efficacy of the protein as a therapeutic agent in situations where the peptide has been generated for that purpose.

Erythropoietin (EPO) is a glycoprotein with three N-glycosylation sites and one O-glycosylation site. Erythropoietin has been manufactured biosynthetically using recombinant DNA technology (Egrie, J C, Strickland, T W, Lane. J et al. (1986) Immunobiol. 72: 213-224) and is the product of a cloned human EPO gene inserted into and expressed in the ovarian tissue cells of the Chinese hamster (CHO cells). The primary structure of the predominant, fully processed form of human erythropoietin (hEPO) is illustrated in FIG. 1. There are two disulfide bridges; between Cys7-Cys161 and Cys29-Cys33. The molecular weight of the polypeptide chain of EPO without the sugar moieties is 18,236 Da. In the intact EPO glycoprotein, approximately 40% of the molecular weight is accounted for by the carbohydrate groups that glycosylate the protein at glycosylation sites on the protein (Sasaki, H, Bothner, B. Dell, A and Fukuda, M (1987) J. Biol. Chem. 262: 12059).

Typical N-glycans of EPO include bi-, tri- and tetraantennary structures with one or two N-acetyl lactosamine repeats (see e.g. Postnikov et al. 2016 Russ. Chem. Rev. 85 99).

It is known that a higher number of terminal sialic acid moieties on N-glycans of EPO is associated with a higher specific activity of EPO when compared to less sialylated EPO glycoproteins (see e.g. Imai et al., Eur. J. Biochem. 194 (1990), p. 457-462). Desialylation of EPO reduces the half-life of EPO in the circulation (Ridley et al. J Natl Med Assoc. 1994 February; 86(2): 129-35).

A higher number of poly-N-acetyl lactosamine repeats or a higher number of branches of the N-glycans of EPO are both reported to be associated with a higher specific bioactivity of EPO, respectively (see e.g. WO 99/28346).

It is known to modify the glycan pattern of EPO using genetically engineered host cells for the production of EPO, e.g. from WO 99/28346.

Methods for modifying the glycan pattern of glycoproteins in vitro, i.e. after production, are suggested. EP 2661492 discloses a method for improving the amount of alpha-2,6-sialylated glycans. EP 2664192 discloses that the circulation time of glycoproteins may be increased by increasing the number of poly-N-acetyl lactosamines, which is suggested to be achieved using a member of the beta3-N-acetyl-glucosamin transferase family (B3GNT1, 2, 3, 4).

WO 2008/57683 discloses a method for purification of EPO. It is suggested to remodel the glycan pattern of EPO in vitro using N-acetyl-glucosamin transferase and galactosyltransferase to form a glycosylated EPO polypeptide having at least one glycan residue with a terminal -GlcNAc-Gal moiety, preferably on mono-antennary branches.

EP 2042196 discloses a method for conjugating glycoproteins, e.g. EPO, with a modifying group (e.g. PEG) via glycan linkage. In order to provide for the optimal glycan pattern for adding the modifying group, the glycan pattern on the glycoprotein may be remodeled using different steps of glycosidation and (re-)glycosylation. In the disclosed method the sugar-coupled modifying group is linked to the glycoprotein using the respective sugar-specific glycosyltransferase. For coupling a sialic-acid-coupled modifying group it is suggested to modify the glycan pattern of EPO, e.g., by (a) sialidation and subsequent sialylation with the sialic-acid-coupled modifying group; (b) treatment with N-acetyl-glucosamin transferase, galactosyltransferase and sialyltransferase ST3; or (c) treatment with sialidase, galactosyltransferase and sialyltransferase ST3.

As the variation of the glycan pattern affects protein function, there is a need for a generally applicable method of producing erythropoiesis stimulating proteins having a desired and reproducible, i.e., a customized glycan pattern, e.g. for assuring a constant quality and/or improving the biological function and/or stability of the erythropoiesis stimulating protein.

SUMMARY OF THE INVENTION

The present invention relates to a method for the production of in vitro glycoengineered erythropoiesis stimulating protein, comprising the steps of

-   -   a) providing sialic acid free erythropoiesis stimulating         protein,     -   b) treating the erythropoiesis stimulating protein with         N-Acetyl-Glucosamin-transferase B3GNT2,     -   c) treating the erythropoiesis stimulating protein with         galactosyltransferase,     -   d) treating the erythropoiesis stimulating protein with         sialyltransferase.

One aspect of the invention relates to the use of the method according to the invention for increasing the number of poly-N-acetyl lactosamine repeats on N-glycans of the erythropoiesis stimulating protein.

Another aspect of the invention is the use of the method according to the invention for providing an erythropoiesis stimulating protein with a controlled number of poly-N-acetyl lactosamine repeats on their N-glycans.

Another aspect of the invention is the use of the method according to the invention for improving the specific activity of the erythropoiesis stimulating protein.

Another aspect of the invention is an in vitro glycoengineered erythropoiesis stimulating protein produced by a method of the invention.

In one embodiment of all aspects of the invention the erythropoiesis stimulating protein is erythropoietin.

The invention provides a method for generating in vitro glycoengineered erythropoiesis stimulating proteins with a controlled number of poly-N-acetyl lactosamine repeats. According to the invention an erythropoiesis stimulating protein can be in vitro glycoengineered resulting in a customized glycan pattern, which may assure a constant product quality and/or improve the biological function, like the specific bioactivity, of the erythropoiesis stimulating protein. With the invention the number of poly-N-acetyl lactosamine repeats on N-glycans of the erythropoiesis stimulating protein can be increased.

DESCRIPTION OF THE FIGURES

FIG. 1: Structure of EPO and its glycosylation sites (adapted from Postnikov et al 2016 Russ. Chem. Rev. 85 99)

FIG. 2A-E: Typical glycosylation patterns of EPO.

FIG. 2A: N-glycan with two branches. FIG. 2B: N-glycan with three branches.

FIG. 2C: N-glycan with four branches. FIG. 2D: N-glycan with four branches and one poly N-acetyl lactosamine repeat. FIG. 2E: N-glycan with four branches and three poly N-acetyl lactosamine repeats.

DETAILED DESCRIPTION OF THE INVENTION 1. Definitions

Unless otherwise defined herein, scientific and technical terms used in connection with the present invention shall have the meanings that are commonly understood by those of ordinary skill in the art. Further, unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular. The methods and techniques of the present disclosure are generally performed according to conventional methods well known in the art. Generally, nomenclatures used in connection with, and techniques of biochemistry, enzymology, molecular, and cellular biology, microbiology, genetics and protein and nucleic acid chemistry and hybridization described herein are those well-known and commonly used in the art.

Unless otherwise defined herein the term “comprising of” shall include the term “consisting of”.

The term “about” as used herein in connection with a specific value (e.g. temperature, concentration, time and others) shall refer to a variation of +/−1% of the specific value that the term “about” refers to.

As used herein, “erythropoiesis stimulating protein” means a protein that directly or indirectly causes activation of the erythropoietin receptor, for example, by binding to and causing dimerization of the receptor. Erythropoiesis stimulating proteins include erythropoietin and variants, analogs, or derivatives thereof that bind to and activate erythropoietin receptor; antibodies that bind to erythropoietin receptor and activate the receptor; or peptides that bind to and activate erythropoietin receptor. The variants, analogs, or derivatives of erythropoietin as meant herein comprise at least three N-glycosylation sites, in one embodiment the N-glycosylation sites are Asn24, Asn38 and Asn83. Erythropoiesis stimulating proteins include, but are not limited to, epoetin alfa, epoetin beta, epoetin delta, epoetin omega, epoetin iota, epoetin zeta, and analogs thereof, pegylated erythropoietin, carbamylated erythropoietin, mimetic peptides (including EMPL/hematide), and mimetic antibodies. Exemplary erythropoiesis stimulating proteins include erythropoietin, darbepoetin, erythropoietin agonist variants, and peptides or antibodies that bind and activate erythropoietin receptor (and include compounds reported in U. S. Patent Application Publication Nos. 2003/0215444 and 2006/0040858, the disclosures of each of which is incorporated herein by reference in its entirety) as well as erythropoietin molecules or variants or analogs thereof as disclosed in the following patents or patent applications, which are each herein incorporated by reference in its entirety: U.S. Pat. Nos. 4,703,008; 5,441,868; 5,547,933; 5,618,698; 5,621,080; 5,756,349; 5,767,078; 5,773,569; 5,955,422; 5,830,851; 5,856,298; 5,986,047; 6,030,086; 6,310,078; 6,391,633; 6,583,272; 6,586,398; 6,900,292; 6,750,369; 7,030,226; 7,084,245; 7,217,689; PCT publication nos. WO 91/05867; WO 95/05465; WO 99/66054; WO 00/24893: WO 01/81405; WO 00/61637: WO 01/36489; WO 02/014356; WO 02/19963; WO 02/20034: WO 02/49673: WO 02/085940; WO 03/029291; WO 2003/055526; WO 2003/084477; WO 2003/094858; WO 2004/002417; WO 2004/002424: WO 2004/009627; WO 2004/024761; WO 2004/033651; WO 2004/035603; WO 2004/043382; WO 2004/101600; WO 2004/101606; WO 2004/101611; WO 2004/106373: WO 2004/018667; WO 2005/001025; WO 2005/001136; WO 2005/021579; WO 2005/025606: WO 2005/032460: WO 2005/051327: WO 2005/063808; WO 2005/063809; WO 2005/070451; WO 2005/081687; WO 2005/084711; WO 2005/103076; WO 2005/100403; WO 2005/092369; WO 2006/50959; WO 2006/02646; WO 2006/29094; and US publication nos. US 2002/0155998; US 2003/0077753; US 2003/0082749; US 2003/0143202; US 2004/0009902; US 2004/0071694 US 2004/0091961; US 2004/0143857; US 2004/0157293; US 2004/0175379; US 2004/0175824; US 2004/0229318; US 2004/0248815; US 2004/0266690; US 2005/0019914; US 2005/0026834; US 2005/0096461; US 2005/0107297; US 2005/0107591; US 2005/0124045; US 2005/0124564; US 2005/0137329; US 2005/0142642; US 2005/0143292; US 2005/0153879; US 2005/0158822; US 2005/0158832; US 2005/0170457; US 2005/0181359; US 2005/0181482; US 2005/0192211; US 2005/0202538; US 2005/0227289; US 2005/0244409; US 2006/0088906; US 2006/0111279.

As used herein, the term “analogs”, when used with reference to polypeptides, refers to an amino acid sequence that has insertions, deletions or substitutions relative to the parent sequence, while still substantially maintaining the biological activity of the parent sequence, as determined using biological assays known to one of skill in the art. As used herein, the term “derivatives” of naturally occurring or analog polypeptides means polypeptides have been chemically modified, for example, to attach water soluble polymers (e.g., pegylated), labels (e.g., radionuclides or various enzymes), or other diagnostic or targeting or therapeutic moieties, or by insertion or substitution of non-natural amino acids by chemical means. Such derivatives will retain the binding properties of underivatized molecules of the invention.

In one embodiment the “erythropoiesis stimulating protein” comprises 3 or more N-glycosylation sites.

In one embodiment the erythropoiesis stimulating protein is erythropoietin.

The term “erythropoietin” or “EPO” refers to a glycoprotein, having the amino acid sequence set out in SEQ ID NO: 1. In one embodiment, this term includes an amino acid sequence substantially homologous to the sequence of SEQ ID NO: 1, whose biological properties relate to the stimulation of red blood cell production and the stimulation of the division and differentiation of committed erythroid progenitors in the bone marrow. As used herein, these terms include such proteins modified deliberately, as for example, by site directed mutagenesis or accidentally through mutations. In an embodiment, the terms erythropoietin or EPO analog include analogs having from 1 to 6 additional sites for glycosylation, analogs having at least one additional amino acid at the carboxy terminal end of the glycoprotein, wherein the additional amino acid includes at least one glycosylation site, and analogs having an amino acid sequence which includes a rearrangement of at least one site for glycosylation. As used herein, “rearrangement” of a glycosylation site means the deletion of one or more glycosylation sites in naturally occurring EPO and the addition of one or more non-naturally occurring glycosylation sites. These terms include both natural and recombinantly produced human erythropoietin.

As used herein, the term “N-glycan” refers to an N-linked oligosaccharide, e.g., one that is attached by an asparagine N-acetylglucosamine linkage to an asparagine residue of a polypeptide. N-glycans have a common pentasaccharide core of Man3GlcNAc2 (“Man” refers to mannose; “Glc” refers to glucose; and “NAc” refers to N-acetyl: “GlcNAc” refers to N-acelylglucosamine). The pentasaccharide core may be fucosylated. The term “trimannose core” used with respect to the N-glycan also refers to the structure Man3GlcNAc2 (“Man3”). N-glycans differ with respect to the number of branches (antennae) comprising peripheral sugars (e.g., fucose [herein abbreviated as “Fuc” ] and sialic acid) that are added to the Man3 core structure. N-glycans are classified according to their branched constituents (e.g., high mannose, complex or hybrid).

Abbreviations used herein, including abbreviations of sugars, are of common usage in the art. Other common abbreviations include “PNGase”, which refers to peptide N-glycosidase F (EC 3.2.2.18). The substrate UDP-GlcNAc is the abbreviation for UDP-N-acetylglucosamine. The intermediate ManNAc is the abbreviation for N-acetylmannosamine. The intermediate ManNAc-6-P is the abbreviation for N-acetylmannosamine-6-phosphate. The intermediate Sia-9-P is the abbreviation for sialate-9-phosphate. The intermediate Cytidine monophosphate-sialic acid is abbreviated as “CMP-Sia.” Sialic acid is abbreviated as “Sia,” “Neu5Ac,” “NeuAc” or “NANA” herein.

The N-glycans on erythropoiesis stimulating proteins, e.g. erythropoietin, include one or more N-acetyl lactosamine units bound to the pentasaccharide core structure of the N-linked oligosaccharide. The number of oligosaccharide “branches” as used herein refers to the number of individual oligosaccharide chains bound to the pentasaccharide core structure. E.g, as demonstrated in FIG. 2A two individual oligosaccharide chains are bound to the pentasaccharide core structure, hence, the N-glycan comprises two branches and is biantennary. E.g, as demonstrated in FIG. 2B three individual oligosaccharide chains are bound to the pentasaccharide core structure, hence, the N-glycan comprises three branches and is triantennary. E.g, as demonstrated in FIG. 2C four individual oligosaccharide chains are bound to the pentasaccharide core structure, hence, the N-glycan comprises four branches and is tetraantennary.

The N-glycans on erythropoiesis stimulating proteins, e.g. erythropoietin, include poly N-acetyl lactosamine units bound to the pentasaccharide core structure of the N-linked oligosaccharide. The term poly N-acetyl lactosamine “repeat” as used herein refers to the number of N-acetyl lactosamine units within one oligosaccharide branch minus one for the first N-acetyl lactosamine unit. E.g, as demonstrated in FIG. 2D two N-acetyl lactosamine units are present within one oligosaccharide branch, meaning that the oligosaccharide comprises one poly N-acetyl lactosamine repeat. E.g, as demonstrated in FIG. 2E four N-acetyl lactosamine units are present within one oligosaccharide branch, meaning that the oligosaccharide comprises three poly N-acetyl lactosamine repeats.

As used herein, the term “sialic acid” refers to a group of molecules where the common molecule includes N-acetyl-5-neuraminic acid (Neu5Ac) having the basic 9-carbon neuraminic acid core modified at the 5-carbon position with an attached acetyl group. Common derivatives of NeuSAc at the 5-carbon position include: 2-keto-3-deoxy-d-glycero-d-galactonononic acid (KDN) which possesses a hydroxyl group in place of the acetyl group; de-N-acetylation of the 5-N-acetyl group produces neuraminic (Neu); hydroxylation of the S—N-acetyl group produces N-glycolylneuraminic acid (Neu5Gc). The hydroxyl groups at positions 4-, 7-, 8- and 9-of these four molecules (NeuSAc, KDN, Neu and Neu5Gc) can be further substituted with O-acetyl, O-methyl, O-sulfate and phosphate groups to enlarge this group of compounds. Furthermore, unsaturated and dehydro forms of sialic acids are known to exist.

The term “sialic acid free” as used herein refers to a population of erythropoiesis stimulating proteins that is substantially free from N-glycans comprising terminal sialic adic moieties. In one embodiment the term “sialic acid free” as used herein refers to a population of erythropoiesis stimulating proteins comprising a relative frequency of N-linked glycans that include a sialic acid moiety of 5% and less. In one embodiment, the sialic acid free erythropoiesis stimulating protein comprises a relative frequency of N-linked glycans that include a sialic acid moiety of about 0%.

The “relative frequency of N-linked glycans” as referred to herein means the percentage of a distinct glycan pattern within the population of erythropoiesis stimulating proteins related to all glycostructures within the population of erythropoiesis stimulating proteins. In one embodiment, the relative frequency of a population of erythropoiesis stimulating proteins refers to the percentage of a distinct glycan pattern within the population of erythropoiesis stimulating proteins related to all glycostructures identified by mass analysis of the entire protein (in one embodiment as described in example 2). In one embodiment, the relative frequency of a population of erythropoiesis stimulating proteins refers to the percentage of a distinct glycan pattern within the population of erythropoiesis stimulating proteins related to all glycostructures identified by mass analysis after enzymatic digest with endoproteinase Glu-C (LCMS peptide mapping, in one embodiment as described in example 1).

The term “in vitro glycoengineering” as referred to herein means the enzymatic alteration of the N-linked glycan structure of a erythropoiesis stimulating protein that is performed in vitro after the erythropoiesis stimulating protein is expressed in a recombinant expression system and, in one preferred embodiment, purified. In vitro glycoengineering within the terms of the invention may encompass the cleavage of at least one sugar residue from the N-linked glycan structure of at least a fraction of the erythropoiesis stimulating proteins comprised within the population of erythropoiesis stimulating proteins that was subject of in vitro glycoengineering. In vitro glycoengineering within the terms of the invention always encompasses also the addition of at least one sugar residue to the N-linked glycan structure of at least a fraction of the glycoproteins comprised within the population of erythropoiesis stimulating proteins that was subject of in vitro glycoengineering.

In vitro glycoengineering within the terms of the invention includes a series of steps of enzymatic treatments of erythropoiesis stimulating proteins that were expressed in a recombinant expressions system and, in one preferred embodiment, purified. In one embodiment said enzymatic treatment includes at least one step of enzymatic treatment with an enzyme capable of cleaving a terminal sugar residue from an N-linked oligosaccharide structure of the eiythropoiesis stimulating protein. In one embodiment, said enzyme is selected a sialidase. In one embodiment said enzymatic treatment includes treatment of the erythropoiesis stimulating protein with a glycosyltransferase, in one preferred embodiment a glycosyltransferase capable of adding a terminal sugar residue to an N-linked oligosaccharide structure of the erythropoiesis stimulating protein. In one embodiment said enzymatic treatment includes treatment of the erythropoiesis stimulating proteins with a N-Acetyl-Glucosamin-transferase, in one preferred embodiment beta-1,3-N-acetylglucosaminyltransferase 2 (B3GNT2). In one embodiment B3GNT2 comprises an amino acid sequence of SEQ ID NO: 2. In one embodiment B3GNT2 consists of an amino acid sequence of SEQ ID NO: 2. In one embodiment said enzymatic treatment includes treatment of the erythropoiesis stimulating proteins with a galactosyltransferase, in one preferred embodiment β1,4-galactosyltransferase 1 (GalT1). In one embodiment GalT1 comprises an amino acid sequence of SEQ ID NO: 3. In one embodiment said enzymatic treatment includes treatment of the erythropoiesis stimulating proteins with a N-sialyltransferase, in one preferred embodiment α2,3-sialyltransferase (ST3) or α2,6-sialyltransferase (ST6). In one embodiment, the N-sialyltransferase is ST3.

The term enzymatically “treating” or enzymatic “treatment” means contacting the erythropoiesis stimulating protein with the respective enzyme in an aqueous solution, preferably a buffered solution.

2. Detailed Description of the Embodiments of the Invention

The invention relates to a method for the production of an in vitro glycoengineered erythropoiesis stimulating protein, comprising the steps of

-   -   a) providing sialic acid free erythropoiesis stimulating         protein,     -   b) treating the erythropoiesis stimulating protein with         N-Acetyl-Glucosamin-transferase B3GNT2.     -   c) treating the erythropoiesis stimulating protein with         galactosyltransferase,     -   d) treating the erythropoiesis stimulating protein with         sialyltransferase.

With the invention, recombinantly produced erythropoiesis stimulating protein is subjected to series of enzymatic treatments in order to provide an erythropoiesis stimulating protein with N-linked glycans comprising a controllable and reproducible number of poly-N-acetyl lactosamine repeats, which can assure a constant product quality and/or improve the biological function of the erythropoiesis stimulating protein. With the invention, the number of poly-N-acetyl lactosamine repeats can be increased compared to the initial erythropoiesis stimulating proteins. The series of enzymatic treatments is performed in the same order as indicated above.

In one embodiment of the invention sialic acid free erythropoiesis stimulating protein that is provided in step a) comprises a relative frequency of N-linked glycans that include a sialic acid of 5%-0%. In one embodiment of the invention sialic acid free erythropoiesis stimulating protein that is provided in step a) comprises a relative frequency of N-linked glycans that include a sialic acid of 2% to 0%. In one embodiment of the invention sialic acid free erythropoiesis stimulating protein that is provided in step a) comprises a relative frequency of N-linked glycans that include a sialic acid of 1% to 0%. In one embodiment of the invention sialic acid free erythropoiesis stimulating protein that is provided in step a) comprises a relative frequency of N-linked glycans that include a sialic acid of about 0%.

In one embodiment of the invention sialic acid free erythropoiesis stimulating protein is provided by treatment of the erythropoiesis stimulating protein with sialidase. In one embodiment sialic acid free erythropoiesis stimulating protein is provided by treatment of the erythropoiesis stimulating protein with sialidase in an aqueous solution at about 37° C. In one embodiment sialic acid free erythropoiesis stimulating protein is provided by treatment of the erythropoiesis stimulating protein with sialidase in an aqueous solution at about 37° C. for 10 to 24 hours. In one embodiment the sialidase is neuraminidase. In one embodiment the neuraminidase is of SEQ ID NO: 6. In one embodiment sialic acid free erythropoiesis stimulating protein is provided by treatment of the erythropoiesis stimulating protein with neuraminidase in an aqueous solution at 35-38° C. In one embodiment sialic acid free erythropoiesis stimulating protein is provided by treatment of the erythropoiesis stimulating protein with neuraminidase in an aqueous solution at about 37° C. In one embodiment sialic acid free erythropoiesis stimulating protein is provided by treatment of the erythropoiesis stimulating protein with neuraminidase in an aqueous solution at about 37° C. for 10 to 24 hours. In one embodiment of the invention, sialidase-treated erythropoiesis stimulating protein is purified prior to the treatment of step b).

In one embodiment the method of the invention comprises the step of providing recombinantly produced erythropoiesis stimulating protein prior to enzymatic treatment. In one preferred embodiment the method comprises the step of providing an erythropoiesis stimulating protein produced in CHO cells prior to enzymatic treatment. Methods for the production of erythropoiesis stimulating proteins in CHO cells are well known in the art (exemplarily for EPO production in CHO cells: EP0205564; EP0148605; Egrie. J C, Strickland, T W. Lane. J et al. (1986) Immunobiol. 72: 213-224; Inoue N, Takeuchi M, Ohashi H. Suzuki T (1995) Biotech Ann Rev. 1: 297-313).

In step b) of the method of the invention GlcNAc is added to the N-linked glycans of the sialic acid free erythropoiesis stimulating protein provided in step a).

In one embodiment of the method of the invention step b) is performed in an aqueous solution in presence of UDP-N-acetylglucosamine. In one embodiment of the method of the invention step b) is performed at pH 7-8, in one embodiment at about pH 7.5. In one embodiment of the method of the invention step b) is performed in presence of manganese ions and calcium ions, in one preferred embodiment in presence of MnCl₂ and CaCl₂). In one embodiment of the method of the invention step b) is performed in a Tris buffered solution of pH 7-8, in presence of NaCl, manganese ions and calcium ions. In one embodiment of the method of the invention step b) is performed in a Tris buffered solution of about pH 7.5, which comprises about 20 to 25 mM Tris, about 100 to 150 mM NaCl, and about 5 to 10 mM MnCl₂ and about 5 to 10 mM CaCl₂. In one embodiment of the method of the invention the treatment of step b) is performed for about 10 to 30 hours, in one preferred embodiment about 16 to about 24 hours. In one embodiment of the method of the invention the treatment of step b) is performed for about 10 to 30 hours at about 37° C.

In one embodiment of the method of the invention the weight ratio between the erythropoiesis stimulating protein and N-Acetyl-Glucosamin-transferase B3GNT2 in step b) is >1:1. In one embodiment of the method of the invention the weight ratio between the erythropoiesis stimulating protein and N-Acetyl-Glucosamin-transferase B3GNT2 in step b) is less than 100:1 and more than 1:1. In one embodiment of the method of the invention the weight ratio between the erythropoiesis stimulating protein and N-Acetyl-Glucosamin-transferase B3GNT2 in step b) is between 2:1 and 1:1. In one embodiment of the method of the invention the weight ratio between the erythropoiesis stimulating protein and N-Acetyl-Glucosamin-transferase B3GNT2 in step b) is about 3:2.

In one embodiment the method of the invention comprises a step of purifying the obtained erythropoiesis stimulating protein after step b) and prior to the treatment with galactosyltransferase. Thereby, the activated sugar substrate for the glycosyltransferase used in step b) is removed. Consequently, further uncontrolled addition of GlcNAc moieties to the erythropoiesis stimulating protein is avoided. This allows a controlled increase of the numbers of poly-N-acetyl lactosamine repeats.

In one embodiment of the method of the invention the step of purifying the obtained erythropoiesis stimulating protein is performed by buffer exchange into an aqueous solution of about pH 6-7, in one preferred embodiment about pH 6.5. In one embodiment the aqueous solution comprises UDP-galactose.

In one embodiment of the method of the invention the step of purifying the obtained erythropoiesis stimulating protein is performed by buffer exchange over a molecular weight cutoff filter of maximal 20 kDa into an aqueous buffer solution of about pH 6.5, wherein the buffer solution comprises about 20 mM manganese ions. In one embodiment the buffer solution comprises about 20 mM MnCl₂. In one embodiment the aqueous solution comprises about 20 mM manganese ions and UDP-galactose.

In step c) of the method of the invention Gal is added to the GlcNAc moieties added to the N-linked glycans in step b).

In one embodiment of the invention the treatment of the erythropoiesis stimulating protein in step c) is with galactosyltransferase GalT1. In one preferred embodiment the treatment of erythropoiesis stimulating protein in step c) is with galactosyltransferase GalT1 of SEQ ID NO. 4.

In one embodiment of the method of the invention step c) is performed using galactosyltransferase GalT1 in presence of UDP-galactose. In one embodiment of the method of the invention step c) is performed in an aqueous buffer solution of pH 6-7, in one preferred embodiment pH about 6.5, wherein the buffer solution comprises about 20 mM mangangese ions, in one preferred embodiment as MnCl₂. In one embodiment of the method of the invention step c) is performed at about 32 to 37° C. In one embodiment of the method of the invention step c) is performed at about 32 to 37° C. for 4 to 10 hours.

In one embodiment of the method of the invention the treatment of step c) is performed for about 2 to 10 hours, in one preferred embodiment about 3 to about 5 hours.

In one embodiment of the method of the invention the weight ratio between the erythropoiesis stimulating protein and galactosyltransferase (in one embodiment GalT1) in step c) is >1:1. In one embodiment of the method of the invention the weight ratio between the erythropoiesis stimulating protein and galactosyltransferase (in one embodiment GalT1) in step c) is between 15:1 and 1:1. In one embodiment of the method of the invention the weight ratio between the erythropoiesis stimulating protein and galactosyltransferase (in one embodiment GalT1) in step c) is between 15:1 and 2:1.

In one embodiment the method of the invention comprises a step of purifying the obtained erythropoiesis stimulating protein after step c) and prior to the treatment with sialyltransferase. Thereby, the activated sugar substrate for the glycosyltransferase used in step c) is removed. Consequently, further uncontrolled addition of Gal moieties to the erythropoiesis stimulating protein is avoided. This allows a controlled increase of the numbers of poly-N-acetyl lactosamine repeats.

In one embodiment the method of the invention comprises a step of purifying the obtained erythropoiesis stimulating protein after step c) and prior to the treatment with sialyltransferase including the step of removing the galactosyltransferase (in one embodiment GalT1). In one embodiment the removal of galactosyltransferase (in one embodiment GalT1) is carried out by ion exchange chromatography. This allows a controlled increase of the numbers of poly-N-acetyl lactosamine repeats and a better substrate conversion in the subsequent sialylation step.

In one embodiment of the method of the invention the step of purifying the obtained erythropoiesis stimulating protein after step c) is performed by buffer exchange into an aqueous solution of about pH 6-7, in one preferred embodiment about pH 6.5. In one embodiment the aqueous solution comprises CMP-N-acetylneuraminic acid.

In one embodiment of the method of the invention the step of purifying the obtained erythropoiesis stimulating protein after step c) is performed by buffer exchange over a molecular weight cutoff filter of maximal 20 kDa into an aqueous buffer solution of about pH 6.5. In one embodiment of the method of the invention the step of purifying the obtained erythropoiesis stimulating protein after step c) is performed by buffer exchange over a molecular weight cutoff filter of maximal 20 kDa into an aqueous buffer solution of about pH 6.5 comprising CMP-N-acetylneuraminic acid.

In step d) of the method of the invention sialic acid is added to the Gal moieties added to the N-linked glycans in step c).

In one embodiment of the method of the invention the treatment of erythropoiesis stimulating protein in step d) is with sialyltransferase ST3. In one preferred embodiment the treatment of erythropoiesis stimulating protein in step d) is with sialyltransferase ST3 of SEQ ID NO: 4. This allows generation of a erythropoiesis stimulating protein with a high relative frequency of alpha-2,3-sialylated N-glycans. The high relative frequency of sialylated N-glycans may additionally contribute to a higher specific bioactivity and a higher serum half life of the erythropoiesis stimulating protein.

In one embodiment of the method of the invention, in one embodiment a method using sialyltransferase ST3 as indicated above, step d) is performed in presence of CMP-N-acetylneuraminic acid. In one embodiment of the method of the invention step d) is performed in an aqueous buffer solution of pH 6-7, in one preferred embodiment pH about 6.5. In one embodiment of the method of the invention step d) is performed for 10 to 20 hours, in one preferred embodiment for about 16 to about 18 hours. In one embodiment of the method of the invention step d) is performed for 10 to 20 hours, in one preferred embodiment for about 16 to about 18 hours at about 37° C. In one embodiment of the method of the invention the weight ratio between erythropoiesis stimulating protein and sialyltransferase (in one embodiment ST3) in step d) is >1:1. In one embodiment of the method of the invention the weight ratio between erythropoiesis stimulating protein and sialyltransferase (in one embodiment ST3) in step d) is between >1:1 and 50:1. In one embodiment of the method of the invention the weight ratio between erythropoiesis stimulating protein and sialyltransferase (in one embodiment ST3) in step d) is between 2:1 and 50:1.

In one embodiment of the invention the treatment of erythropoiesis stimulating protein in step d) is with sialyltransferase ST6. In one preferred embodiment the treatment of erythropoiesis stimulating protein in step d) is with sialyltransferase ST6 of SEQ ID NO: 5.

The invention also relates to the use of the method of the invention for increasing the number of poly-N-acetyl lactosamine repeats on N-glycans of an erythropoiesis stimulating protein.

Another aspect of the invention is the method of the invention for increasing the number of poly-N-acetyl lactosamine repeats on N-glycans of an erythropoiesis stimulating protein.

Another aspect of the invention is the use of the method of the invention for providing an erythropoiesis stimulating protein with a controlled number of poly-N-acetyl lactosamine repeats on N-glycans of the erythropoiesis stimulating protein. In one embodiment the method is used for providing erythropoiesis stimulating protein with up to 15 poly-N-acetyl lactosamine repeats per N-glycosylation site. In one embodiment the method is used for providing erythropoiesis stimulating protein with 2-15 poly-N-acetyl lactosamine repeats per N-glycosylation site. In one embodiment the method is used for providing erythropoiesis stimulating protein with 2-12 poly-N-acetyl lactosamine repeats per N-glycosylation site. In one embodiment the method is used for providing erythropoiesis stimulating protein with 4-10 poly-N-acetyl lactosamine repeats per N-glycosylation site.

In one embodiment the method is used for providing erythropoiesis stimulating protein with up to 15 poly-N-acetyl lactosamine repeats per erythropoiesis stimulating protein. In one embodiment the method is used for providing erythropoiesis stimulating protein with 2-15 poly-N-acetyl lactosamine repeats per erythropoiesis stimulating protein.

Another aspect of the invention is the use of the method of the invention for improving the specific activity of the erythropoiesis stimulating protein.

Another aspect of the invention is an in vitro glycoengineered erythropoiesis stimulating protein produced by a method of the invention.

Another aspect of the invention is a population of erythropoiesis stimulating proteins, characterized in that the relative frequency of N-linked glycans comprising more than two poly-N-acetyl lactosamine repeats on each N-glycosylation site is more than 90%, in one embodiment more than 99%, in one embodiment about 100%, in one embodiment exactly 100%.

Within the population of erythropoiesis stimulating proteins of the invention all erythropoiesis stimulating proteins comprise 2 or more poly-N-acetyl lactosamine repeats. Consequently, the population of erythropoiesis stimulating proteins of the invention is free of erythropoiesis stimulating proteins with zero or one poly-N-acetyl lactosamine repeats. In this connection, “free” (of erythropoiesis stimulating proteins with zero or one poly-N-acetyl lactosamine repeats) refers to a fraction of 0,1% and less, in one embodiment to a fraction of 0%. The term “fraction” in this refers to the number of molecules in the sample, e.g. a fraction of 1% means one erythropoiesis stimulating protein out of 100 erythropoiesis stimulating protein molecules.

Another aspect of the invention is a population of erythropoiesis stimulating proteins, characterized in that the average number of poly-N-acetyl lactosamine repeats per individual erythropoiesis stimulating protein is at least 10. In one embodiment the average number of poly-N-acetyl lactosamine repeats per erythropoiesis stimulating protein is 10 to 4).

In one embodiment, the population of erythropoiesis stimulating proteins of the invention is characterized in that the relative frequency of N-linked glycans comprising more than two poly-N-acetyl lactosamine repeats on each N-glycosylation site is more than 99%, in one embodiment about 100%, in one embodiment exactly 100%; and the average number of poly-N-acetyl lactosamine repeats per erythropoiesis stimulating protein is more than 10, in one embodiment 10 to 40. In one embodiment the average number of poly-N-acetyl lactosamine repeats per N-glycosylation site is at least 2. In one embodiment the average number of poly-N-acetyl lactosamine repeats per N-glycosylation site is at least 3.

In one embodiment the population of erythropoiesis stimulating proteins is produced by a method of the invention.

3. Specific Embodiments of the Invention

In the following specific embodiments of the invention are listed.

-   -   1. A method for the production of in vitro glycoengineered         erythropoiesis stimulating protein, comprising the steps of         -   a) providing sialic acid free erythropoiesis stimulating             protein,         -   b) treating the erythropoiesis stimulating protein with             N-Acetyl-Glucosamin-transferase B3GNT2,         -   c) treating the erythropoiesis stimulating protein with             galactosyltransferase,         -   d) treating the erythropoiesis stimulating protein with             sialyltransferase.     -   2. The method of embodiment 1, wherein the erythropoiesis         stimulating protein is erythropoietin.     -   3. The method of any one of the preceding embodiments,         characterized in that step b) is performed in an aqueous         solution in presence of UDP-N-acetylglucosamine.     -   4. The method of any one of the preceding embodiments,         characterized in that step b) is performed at pH 7-8.     -   5. The method of any one of the preceding embodiments,         characterized in that step b) is performed at about pH 7.5.     -   6. The method of any one of the preceding embodiments,         characterized in that step b) is performed in presence of         manganese ions and calcium ions.     -   7. The method of any one of the preceding embodiments,         characterized in that step b) is performed in presence of MnCl₂         and CaCl₂).     -   8. The method of one of embodiments 1 to 4, characterized in         that step b) is performed in a Tris buffered solution of pH 7-8,         in presence of NaCl, manganese ions and calcium ions.     -   9. The method of any one of the preceding embodiments,         characterized in that step b) is performed in a Tris buffered         solution of about pH 7.5, which comprises about 25 mM Tris,         about 150 mM NaCl, and about 10 mM MnCl₂ and about 10 mM CaCl₂.     -   10. The method of any one of the preceding embodiments, wherein         the treatment of step b) is performed for about 10 to 30 hours.     -   11. The method of any one of the preceding embodiments, wherein         the treatment of step b) is performed for about 16 to about 24         hours.     -   12. The method of any one of the preceding embodiments, wherein         the treatment of step b) is performed at about 37° C.     -   13. The method of any one of the preceding embodiments, the         weight ratio between erythropoiesis stimulating protein and         N-Acetyl-Glucosamin-transferase B3GNT2 in step b) is >1:1.     -   14. The method of any one of the preceding embodiments,         characterized in that the method comprises a step of purifying         the obtained erythropoiesis stimulating protein after step b)         and prior to the treatment with galactosyltransferase.     -   15. The method of embodiment 14, wherein the step of purifying         the obtained erythropoiesis stimulating protein is performed by         buffer exchange into an aqueous solution of about pH 6-7     -   16. The method of embodiment 14, wherein the step of purifying         the obtained erythropoiesis stimulating protein is performed by         buffer exchange into an aqueous solution of about pH 6.5.     -   17. The method of one of embodiments 14 to 16, wherein the step         of purifying the obtained erythropoiesis stimulating protein is         performed by buffer exchange over a molecular weight cutoff         filter of maximal 20 kDa into an aqueous buffer solution of         about pH 6.5, wherein the buffer solution comprises about 20 mM         manganese ions.     -   18. The method of embodiment 17, wherein the buffer solution         comprises about 20 mM MnCl₂.     -   19. The method of embodiment 17 or 18, wherein the buffer         solution comprises UDP-galactose.     -   20. The method of any one of the preceding embodiments,         characterized in that step c) is performed using         galactosyltransferase GalT1 in presence of UDP-galactose.     -   21. The method of embodiment 20, characterized in that step c)         is performed in an aqueous buffer solution of pH 6-7, wherein         the buffer solution comprises mangangese ions.     -   22. The method of embodiment 21, wherein the buffer solution has         a pH of about 6.5.     -   23. The method of embodiments 21 or 22, wherein the buffer         solution comprises 20 mM mangangese ions.     -   24. The method of one of embodiments 21 to 23, wherein the         buffer solution comprises MnCl₂.     -   25. The method of one of embodiments 20 to 24, wherein the         treatment of step c) is performed for about 2 to 10 hours     -   26. The method of one of embodiments 20 to 24, wherein the         treatment of step c) is performed for about 3 to about 5 hours.     -   27. The method of one of embodiments 20 to 26, wherein the         weight ratio between erythropoiesis stimulating protein and         galactosyltransferase in step c) is >1:1.     -   28. The method of any one of the preceding embodiments,         characterized in that the method comprises a step of purifying         the obtained erythropoiesis stimulating protein after step c)         and prior to the treatment with sialyltransferase.     -   29. The method of embodiment 28, wherein the step of purifying         the obtained erythropoiesis stimulating protein is performed by         buffer exchange into an aqueous solution of about pH 6-7.     -   30. The method of embodiment 28, wherein the step of purifying         the obtained erythropoiesis stimulating protein is performed by         buffer exchange into an aqueous solution of about pH 6.5.     -   31. The method of one of embodiments 28 to 30, wherein step of         purifying the obtained erythropoiesis stimulating protein is         performed by buffer exchange over a molecular weight cutoff         filter of maximal 20 kDa into an aqueous buffer solution of         about pH 6.5.     -   32. The method of one of embodiments 29 to 31, wherein the         aqueous solution comprises CMP-N-acetylneuraminic acid.     -   33. The method of any one of the preceding embodiments,         characterized in that step d) is performed using         sialyltransferase ST3.     -   34. The method of embodiment 33, characterized in that step d)         is performed in presence of CMP-N-acetylneuraminic acid.     -   35. The method of embodiment 33 or 34, wherein step d) is         performed in an aqueous buffer solution of pH 6-7.     -   36. The method of embodiment 33 or 34, wherein step d) is         performed in an aqueous buffer solution of about pH 6.5.     -   37. The method of one of embodiments 33 to 36, wherein step d)         is performed for 10 to 20 hours.     -   38. The method of one of embodiments 33 to 36, wherein step d)         is performed for about 16 to about 18 hours.     -   39. The method of one of embodiments 33 to 38, wherein step d)         is performed at about 37° C.     -   40. The method of one of embodiments 33 to 39, wherein invention         the weight ratio between erythropoiesis stimulating protein and         sialyltransferase in step d) is >1:1.     -   41. The method of any one of the preceding embodiments, wherein         the sialic acid free erythropoiesis stimulating protein         comprises a relative frequency of N-linked glycans that include         a sialic acid of 5%-0%.     -   42. The method of any one of the preceding embodiments, wherein         the sialic acid free erythropoiesis stimulating protein         comprises a relative frequency of N-linked glycans that include         a sialic acid of 2%-0%.     -   43. The method of any one of the preceding embodiments, wherein         the sialic acid free erythropoiesis stimulating protein         comprises a relative frequency of N-linked glycans that include         a sialic acid of 1%-0%.     -   44. The method of any one of the preceding embodiments, wherein         the sialic acid free erythropoiesis stimulating protein         comprises a relative frequency of N-linked glycans that include         a sialic acid of about 0%.     -   45. The method of any one of the preceding embodiments,         characterized in that sialic acid free erythropoiesis         stimulating protein is provided by treatment of erythropoiesis         stimulating protein with sialidase.     -   46. The method of any one of the preceding embodiments,         comprising the step of providing erythropoiesis stimulating         protein produced in CHO cells prior to enzymatic treatment.     -   47. Use of the method of any one of the preceding embodiments         for increasing the number of poly-N-acetyl lactosamine repeats         on the N-glycans of the erythropoiesis stimulating protein.     -   48. Use of the method of one of embodiments 1 to 46 for         providing an erythropoiesis stimulating protein with a         controlled number of poly-N-acetyl lactosamine repeats on their         N-glycans.     -   49. Use of the method of one of embodiments 1 to 46 for         providing erythropoiesis stimulating protein with up to 15         poly-N-acetyl lactosamine repeats per N-glycosylation site.     -   50. The use of embodiment 49 for providing erythropoiesis         stimulating protein with 2 or more poly-N-acetyl lactosamine         repeats per N-glycosylation site.     -   51. Use of the method of one of embodiments 1 to 46 for         improving the specific activity of the erythropoiesis         stimulating protein.     -   52. In vitro glycoengineered erythropoiesis stimulating protein         produced by a method of any one of embodiments 1 to 46.     -   53. In vitro glycoengineered erythropoietin produced by a method         of any one of embodiments 1 to 46.     -   54. A population of erythropoiesis stimulating proteins,         characterized in that the relative frequency of N-linked glycans         comprising more than two poly-N-acetyl lactosamine repeats on         each N-glycosylation site is more than 90%.     -   55. The population of erythropoiesis stimulating proteins of         embodiment 54, wherein the relative frequency of N-linked         glycans comprising more than two poly-N-acetyl lactosamine         repeats on each N-glycosylation site is more than 99%.     -   56. The population of erythropoiesis stimulating proteins of         embodiment 54, wherein the relative frequency of N-linked         glycans comprising more than two poly-N-acetyl lactosamine         repeats on each N-glycosylation site is about 100%.     -   57. The population of erythropoiesis stimulating protein         proteins of embodiment 54, wherein the relative frequency of         N-linked glycans comprising more than two poly-N-acetyl         lactosamine repeats on each N-glycosylation site is exactly         100%.     -   58. The population of erythropoiesis stimulating proteins of one         of embodiments 54 to 57, wherein the population of         erythropoiesis stimulating proteins is free of erythropoiesis         stimulating proteins with zero or one poly-N-acetyl lactosamine         repeats.     -   59. The population of erythropoiesis stimulating proteins of one         of embodiments 54 to 57, wherein the population of         erythropoiesis stimulating proteins comprises a fraction of 0,1%         and less of erythropoiesis stimulating proteins with zero or one         poly-N-acetyl lactosamine repeats.     -   60. The population of erythropoiesis stimulating proteins of one         of embodiments 54 to 57, wherein the population of         erythropoiesis stimulating proteins comprises a fraction of 0%         of erythropoiesis stimulating proteins with zero or one         poly-N-acetyl lactosamine repeats.     -   61. The population of erythropoiesis stimulating proteins of one         of embodiments 54 to 60, wherein that the average number of         poly-N-acetyl lactosamine repeats per individual erythropoiesis         stimulating protein is at least 4.     -   62. The population of erythropoiesis stimulating proteins of one         of embodiments 54 to 60, wherein that the average number of         poly-N-acetyl lactosamine repeats per individual erythropoiesis         stimulating protein is at least 10.     -   63. The population of erythropoiesis stimulating proteins of one         of embodiments 54 to 62, wherein that the average number of         poly-N-acetyl lactosamine repeats per individual erythropoiesis         stimulating protein is up to 40.     -   64. The population of erythropoiesis stimulating proteins of one         of embodiments 54 to 63, wherein the erythropoiesis stimulating         protein is erythropoietin.

DESCRIPTION OF THE AMINO ACID SEQUENCES

SEQ ID NO: 1 erythropoietin 165 aa APPRLICDSRVLERYLLEAKEAENITTGCAEHCSLNENITVPDTKVNFYAW KRMEVGQQAVEVWQGLALLSEAVLRGQALLVNSSQPWEPLQLHVDKAVSGL RSLTTLLRALGAQKEAISPPDAASAAPLRTITADTFRKLFRVYSNFLRGKL KLYTGEACRTGD SEQ ID NO: 2 N-Acetyl-Glucosamin-transferase B3GNT2 MVSRSLVGILMMANVFIYFIMEVSKSSSQEKNGKGEVIIPKEKFWKISTPP EAYWNREQEKLNRQYNPILSMLTNQTGEAGRLSNISHLNYCEPDLRVTSVV TGFNNLPDRFKDFLLYLRCRNYSLLIDQPDKCAKKPFLLLAIKSLTPHFAR RQAIRESWGQESNAGNQTVVRVFLLGQTPPEDNHPDLSDMLKFESEKHQDI LMWNYRDTFFNLSLKEVLFLRWVSTSCPDTEFVFKGDDDVFVNTHHILNYL NSLSKTKAKDLFIGDVIHNAGPHRDKKLKYYIPEVVYSGLYPPYAGGGGFL YSGHLALRLYHITDQVHLYPIDDVYTGMCLQKLGLVPEKHKGFRTFDIEEK NKNNICSYVDLMLVHSRKPQEMIDIWSQLQSAHLKC SEQ ID NO: 3 galactosyltransferase GalT1 MGVHECPAWLWLLLSLLSLPLGLPVLGAPRDLSRLPQLVGVSTPLQGGSNS AAAIGQSSGELRTGGARPPPPLGASSQPRPGGDSSPVVDSGPGPASNLTSV PVPHTTALSLPACPEESPLLVGPMLIEFNMPVDLELVAKQNPNVKMGGRYA PRDCVSPHKVAIIIPFRNRQEHLKYWLYYLHPVLQRQQLDYGIYVINQAGD TIFNRAKLLNVGFQEALKDYDYTCFVFSDVDLIPMNDHNAYRCFSQPRHIS VAMDKFGFSLPYVQYFGGVSALSKQQFLTINGFPNNYWGWGGEDDDIFNRL VFRGMSISRPNAVVGRCRMIRHSRDKKNEPNPQRFDRIAHTKETMLSDGLN SLTYQVLDVQRYPLYTQITVDIGTPS SEQ ID NO: 4 human α2,3-sialyltransferase (ST3) MGVHECPAWLWLLLSLLSLPLGLPVLGVAPVEMKRRNKIQPCLSKPAFASL LRFHQFHPFLCAADRFKIASLYGSDKFDLPYGMRTSAEYFRLALSKLQSCD LFDEFDNIPCKKCVVVGNGGVLKNKTLGEKIDSYDVIIRMNNGPVLGHEEE VGRRTTFRLFYPESVFSDPIHNDPNTTVILTAFKPHDLRWLLELLMGDKIN TNGFWKKPALNLIYKPYQIRILDPFIIRTAAYELLHFPKVFPKNQKPKHPT TGIIAITLAFYICHEVHLAGFKYNFSDLKSPLHYYGNATMSLMNKNAYHNV TAEQLFLKDIIEKNLVINLTQD SEQ ID NO: 5 human, α2,6-sialyltransferase (ST6) MGVHECPAWLWLLLSLLSLPLGLPVLGAPEASFQVWNKDSSSKNLIPRLQK IWKNYLSMNKYKVSYKGPGPGIKFSAEALRCHLRDHVNVSMVEVTDFPFNT SEWEGYLPKESIRTKAGPWGRCAVVSSAGSLKSSQLGREIDDHDAVLRFNG APTANFQQDVGTKTTIRLMNSQLVTTEKRFLKDSLYNEGILIVWDPSVYHS DIPKWYQNPDYNFFNNYKTYRKLHPVQPFYILKPQMPWELWDILQEISPEE IQPNPPSSGMLGIIIMMTLCDQVDIYEFLPSKRKTDVCYYYQKFFDSACTM GAYHPLLYEKNLVKHLNQGTDEDIYLLGKATLPGFRTIHC

EXAMPLES

The following examples are provided to aid the understanding of the present invention, the true scope of which is set forth in the appended claims. It is understood that modifications can be made in the procedures set forth without departing from the spirit of the invention.

Example 1 Increase of Number of Poly-N-Acetyl Lactosamine Repeats by In Vitro Glycoengineering of EPO (No Purification Between B3Gnt2 and GalT1 Treatments)

Erythropoietin (EPO) was provided by recombinant production in CHO cells (see also EP0205564; EP0148605).

In vitro glycoengineering (IVGE) treatment of the recombinant EPO was performed as follows:

EPO was desialylated by incubation with neuraminidase (Roche) in aqueous buffered solution of pH 7.5 at 37° C. for 18 hours.

For addition of GlcNAc moieties to the N-linked glycans 1.5 mg desialylated erythropoietin were mixed with 1.0 mg N-acetylglucosamine transferase, B3GnT2 (dissolved in 25 mM Tris, 150 mM NaCl, pH7.5). 8.8 mg UDP-N-acetylglucosamine, 2.5 mg MnCl₂ and 2.2 mg CaCl₂) (each dissolved in water) were added to the solution. The sample was incubated at 37° C. for 24 hours.

Subsequently for addition of Gal moieties to the N-linked glycans 149 j g galactosyltransferase, GalT1 and 3 mg UDP-galactose were added, followed by incubation at 37° C. for 5 hours.

Finally, 54 μg sialyltransferase, ST3, 70 mg CMP-N-acetyl-neuraminic acid, 17 μg alkaline phosphatase and 20 μl of 10 mM ZnCl₂ solution were added and incubated at 37° C. for 18 hours.

The analysis of glycostructures present on the N-linked glycans of the obtained in vitro glycoengineered erythropoietin was performed by LCMS peptide mapping after endoproteinase Glu-C digest. For this, 250 μg sample were denatured (using guanidinium hydrochloride), reduced (using dithiothreitol), carboxymethylated (using iodoacetic acid) and finally digested by endoproteinase Glu-C. The digest was analyzed by RP-UHPLC with an online coupled mass spectrometer. Resulting data sets were evaluated for specific glycan signal of the peptides bearing the N-glycosylation sites (asparagine 24, 38 and 83).

Results are shown in the following tables comparing recombinantly produced erythropoietin that was not treated with any glycosidase or glycosyltransferase (“EPO before IVGE”) and erythropoietin resulting from a method of the invention as described before (“EPO after IVGE”). The term “repeat” refers to the poly N-acetyl lactosamine repeat as defined above.

TABLE 1 EPO before IVGE (comparative data) Indicated is the fraction of erythropoietin glycoproteins comprising 0, 1, 2 or more than 2 poly N-acetyl lactosamine repeats at the respective N-glycan present at the indicated N-glycosylation site. 0 repeats 1 repeat 2 repeats >2 repeats [%] [%] [%] [%] Asn 24 76 18 6 0 Asn 38 66 27 7 0 Asn 83 64 28 8 0

TABLE 2 EPO before IVGE (comparative data) average number of repeats per EPO molecule: ~1 fraction of EPO molecules with 1 and less repeats: 79% fraction of EPO molecules with 2 and more repeats: 21%

TABLE 3 EPO after IVGE Indicated is the fraction of erythropoietin glycoproteins comprising 0, 1, 2, or more than 2 poly N-acetyl lactosamine repeats at the respective N-glycan present at the indicated N-glycosylation site. 0 repeats 1 repeat 2 repeats >2 repeats [%] [%] [%] [%] Asn 24 0 0 0 100 Asn 38 0 0 0 100 Asn 83 0 0 0 100

TABLE 4 EPO after IVGE Indicated is the minimal number and the range of the number of poly N-acetyl lactosamine repeats at the respective N-glycan present at the indicated N-glycosylation site. minimal # repeats range of # of repeats Asn 24 4 4-12 Asn 38 8 8-13 Asn 83 8 8-12

TABLE 5 EPO after IVGE average number of repeats per EPO molecule: ≥20 fraction of EPO molecules with 1 and less repeats:  0 fraction of EPO molecules with 2 and more repeats: 100%

The results indicate that the IVGE procedure results in a population of EPO molecules, wherein all individual EPO molecules comprise several poly N-acetyl lactosamine repeat on each N-glycosylation site. All EPO molecules comprise at least 20 poly N-acetyl lactosamine repeats per molecule.

Untreated CHO produced EPO comprises a fraction of 79% of individual molecules with zero or one poly N-acetyl lactosamine repeats per EPO molecule.

Example 2 Controlled Number of Poly-N-Acetyl Lactosamine Repeats by In Vitro Glycoengineering of EPO (Purification Steps Between B3Gnt2 and GalT1 Treatment and Between GalT1 and ST3 Treatment)

Erythropoietin (EPO) was provided by recombinant production in CHO cells as in Example 1.

In vitro glycoengineering (IVGE) treatment of the recombinant EPO was performed as follows:

EPO was desialylated as described in Example 1.

For addition of GlcNAc moieties to the N-linked glycans 90 μg of the desialylated erythropoietin glycoproteins were mixed with 60 μg N-acetylglucosamine transferase B3GnT2 (dissolved in 25 mM Tris, 150 mM NaCl, pH7.5), and 525 μg UDP-N-acetylglucosamine in 25 mM Tris buffer including 10 mM CaCl₂ and 10 mM MnCl₂ at pH 7.5. The sample was incubated at 37° C. for 16 hours. One third of the sample containing EPO glycoproteins was used for analytical purposes.

Residual material of the EPO glycoproteins was purified by buffer exchange to 100 mM MES buffer including 20 mM MnCl₂ and 20 mM UDP-galactose at pH 6.5 using Vivaspin centrifugation columns (10 kD filter).

For addition of Gal moieties to the N-linked glycans 27 μg galactosyltransferase, GalT1, was added to the EPO glycoproteins sample, which was subsequently incubated at 32° C. for 4 hours. Subsequently, half of the material was used for analytical purposes.

Residual material of the EPO glycoproteins was purified by buffer exchange to 100 mM MES. pH6.5, incl. 150 mg/ml CMP-N-acetyl-neuraminic acid. 27 μg sialyltransferase, ST3, were added followed by incubation at 37° C. for 16 hours.

The analysis of glycostructures present on the N-linked glycans of the obtained in vitro glycoengineered erythropoietin was performed by mass spectrometry. For this, samples were injected in a UHPLC system without further sample preparation. The UHPLC system was coupled to a mass spectrometer. Data sets (deconvoluted sum spectra) were evaluated with regard to glycan specific signals.

Results are shown in the following data sets comparing recombinantly produced erythropoietin that was not treated with any glycosidase or glycosyltransferase (“EPO before IVGE”) and erythropoietin resulting from a method of the invention as described before (“EPO after IVGE”). The term “repeat” refers to the poly N-acetyl lactosamine repeat as defined above.

TABLE 6 EPO before IVGE (comparative data) average number of repeats per EPO molecule: ~1 fraction of EPO molecules with 1 and less repeats: 80% fraction of EPO molecules with 2 and more repeats: 20%

TABLE 7 EPO after IVGE average number of repeats per EPO molecule: ≥12 fraction of EPO molecules with 1 and less repeats:  0% fraction of EPO molecules with 2 and more repeats: 100%

Untreated CHO produced EPO comprised a fraction of 80% of individual molecules with zero or one poly N-acetyl lactosamine repeats per EPO molecule, while in vitro glycoengineered EPO comprised 100% of EPO glycoproteins with 2 and more poly N-acetyl lactosamine repeats. The average number of poly N-acetyl lactosamine repeats per EPO glycoprotein is 12 and more, whereas untreated CHO produced EPO comprised about 1 poly N-acetyl lactosamine repeat per EPO glycoprotein. 

1. A method for the production of an in vitro glycoengineered erythropoiesis stimulating protein, comprising the steps of a) providing sialic acid free erythropoiesis stimulating protein, b) treating the erythropoiesis stimulating protein with N-Acetyl-Glucosamin-transferase B3GNT2, c) treating the erythropoiesis stimulating protein with galactosyltransferase, d) treating the erythropoiesis stimulating protein with sialyltransferase.
 2. The method of claim 1, characterized in that step b) is performed in presence of manganese ions and calcium ions.
 3. The method of claim 1, the weight ratio between erythropoiesis stimulating protein and N-Acetyl-Glucosamin-transferase B3GNT2 in step b) is >1:1.
 4. The method of claim 1, characterized in that the method comprises a step of purifying the obtained erythropoiesis stimulating protein after step b) and prior to the treatment with galactosyltransferase.
 5. The method of claim 1, characterized in that step c) is performed using galactosyltransferase GalT1 in presence of UDP-galactose.
 6. The method of claim 1, characterized in that the method comprises a step of purifying the obtained erythropoiesis stimulating protein after step c) and prior to the treatment with sialyltransferase.
 7. The method of claim 1, characterized in that step d) is performed using sialyltransferase ST3.
 8. The method of claim 1, wherein the sialic acid free erythropoiesis stimulating protein comprises a relative frequency of N-linked glycans that include a sialic acid of 2%-0%.
 9. Use of the method of claim 1 for increasing the number of poly-N-acetyl lactosamine repeats on the N-glycans of the erythropoiesis stimulating protein.
 10. Use of the method of claim 1 for providing erythropoiesis stimulating protein with 2 or more poly-N-acetyl lactosamine repeats per N-glycosylation site.
 11. In vitro glycoengineered erythropoiesis stimulating protein, wherein the average number of poly-N-acetyl lactosamine repeats per erythropoiesis stimulating protein is more than 10, produced by a method of any one of claims 1 to
 8. 12. A population of erythropoiesis stimulating proteins, characterized in that the relative frequency of N-linked glycans comprising more than two poly-N-acetyl lactosamine repeats on each N-glycosylation site is more than 90%, and characterized in that the average number of poly-N-acetyl lactosamine repeats per erythropoiesis stimulating protein is more than
 10. 13. The population of erythropoiesis stimulating proteins of claim 12, wherein the population of erythropoiesis stimulating proteins is free of erythropoiesis stimulating proteins with zero or one poly-N-acetyl lactosamine repeats.
 14. The method of claim 1, the use of claim 9 or 10, the in vitro glycoengineered erythropoiesis stimulation protein of claim 11, or the population of erythropoiesis stimulating proteins of one of claim 12 or 13, wherein the erythropoiesis stimulating protein is erythropoietin.
 15. Use of the method of claim 1 for improving the specific activity of the erythropoiesis stimulating protein. 